The β-model Problem: The Incompatibility of X-ray and Sunyaev-Zeldovich Effect Model Fitting for Galaxy Clusters

Introduction: We describe an analysis of a large sample of numerically simulated clusters which demonstrates the effects of using X-ray fitted βmodel parameters with Sunyaev-Zeldovich effect (SZE) data. There is a fundamental incompatibility between β fits to X-ray surface brightness profiles and those done with SZE profiles. Since observational SZE radial profiles are in short supply, the X-ray parameters are often used in SZE analysis. We show that this leads to biased estimates of the integrated SZE inside r500 (represented here by y500 ) calculated from clusters. The correlation between y500 and cluster total mass is very tight, and is a promising tool for cluster cosmology. We suggest a simple correction of the method, using a nonisothermal β-model modified by a universal temperature profile (UTP), which brings these calculated quantities into closer agreement with the true values. Jack O. Burns1, Eric J. Hallman1, Patrick M. Motl2, Michael L. Norman3 1Univ. Of Colorado at Boulder, 2Louisana State University, 3Univ. of California at San Diego. Department of Astrophysical and Planetary Sciences University of Colorado